volvo model 2003 misfiring

I have a 3 cyl volvo model 2003, engine is approx 25 years old. Has started to put out white smoke with unburnt diesel in the exhaust. It is not going through coolant and the oil appears clean so i dont think it is a head gasket or anything related to that. After changing all the filters and no improvement i decided the test the individual cylinders by opening the fuel pipe nut at the injector to see if all the cylinders where firing properly. When i did the test to the first and third cylinders the engine ran really rough and nearly died but when i tried it on the 2nd cylinder the engine did not change. I did these individually and allowed the engine to get back to "normal" between tests. What is the likely cause of this misfiring? Does it mean its time to call the mechanic to pull the injectors?

Thanks for the help

G'day,
Sounds like either a crook injector or a compression problem such as a u/s valve, my money would be on a bad injector. Try swapping the injector from cyl #2 cyl to #1 or 3 if symptom moves you have a crook injector if no change time for a compression test.

Greetings.
I have the same engine and had what sounds like a similar problem in terms of the white smoke.

In the end I removed the exhaust outlet elbow and found it was absolutely coked up such that all the water pathways (except the one from the thermostat) were blocked. How it had been working is beyond me.

The casting has a few internal water jet pathways (where the cooling water gets injected into the exhaust) and a cooling jacket all cast in place as it is manufactured. All these were full of hard carbon deposite which was hard to distinguish from the casting itself!
I spent a few mucky hours digging it all out with a dremel (nasty dust by the way) and the problem pretty much went away.

not an identical problem, but my solution might be worth considering.